Layer-by-layer self-assembly
Layer-by-layer deposition is a self-assembly techniques used for the production of organic multilayered structures on a solid surface. In most cases, electrostatic forces are used to adsorb an utltrathin layer of a charged specie (a ployelectrolyte, namely a polymer containing ionic or ionizable groups) that compensates the net charge of the underlying structure. After a washing step, the system is ready to adsorb a new layer of opposite charge. Alternating cationic and anionc layers can be deposited in this way on the surface of various substrates, including nanoparticles. Even if the driving force for self-assembly is Coulombic, the binding interaction between the layers is not solely electrostatic.
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Cartoon representation of layer-by-layer self-assembly. The brown molecules are anchored on functional groups attached to a solid surface. The decorated surface is put in a solution where the yellow molecules find their way to the brown molecules, thanks to the assumed attractive force between the green balls and the red balls. Once a first bilayer has been formed on the surface, the process can be repeated several times to deposit as many bilayers. |
Efficient electrochromic composite films can be fabricated by layer-by-layer deposition of electrochromic polyelectrolytes.